<html>
<head>
    <script>
        // 不兼容 performance.timing 的浏览器
        window.pageStartTime = Date.now()
    </script>
    <script>
        // 白屏结束时间
        window.firstPaint = Date.now()
        // 白屏时间
        console.log(firstPaint - performance.timing.navigationStart)
    </script>
</head>
<body>
<div id="root">root</div>
<style>
    div {
        color: lightgrey;
    }
</style>
<script src="./aboveTheFold.js"></script>
<style>
    div {
        color: green;
    }
</style>
</body>
</html>
